A significant trend in the electronics industry is the downward size scaling of integrated circuits. Reducing the size of transistors in an integrated circuit enables reduced cost, improved performance, and more complex integrated circuits.
The trend of reducing transistor size, however, may be approaching significant limitations. A particular concern is the gate leakage currents of the widely prevalent metal-oxide-semiconductor field-effect transistors (MOSFETs). MOSFETs are a mainstay of the microelectronics industry and are widely used, particularly as complementary pairs within digital logic circuits. Unfortunately, as MOSFETs are scaled down, gate leakage currents rise exponentially with decreasing gate oxide (insulator) thickness. While various techniques, such as substituting higher dielectric constant materials for the gate insulator, and increasing the gate insulator thickness relative to other dimensions can mitigate some of the problems, gate leakage current-density in small MOSFETs (e.g., 35 nm and below) may become problematic. Modifications to MOSFET designs to address gate leakage can also involve additional complex processing steps, increasing costs, and making scaling less viable. Accordingly, scaling down MOSFETs has become increasingly difficult and expensive.